The present invention relates to a test method for an escape path marking.
When utilising non-electric escape path markings, in particular if they are not charged by daylight, but by means of an artificial light source, it is to be ensured that the escape path marking possesses sufficient afterglow time. For use in aircraft, evidence needs to be provided that the escape path marking has sufficient afterglow time to be able to adequately light up the escape paths in the aircraft cabin in an emergency.
If an airline would like to install a non-electric escape path marking in an aircraft, first of all photometry is to be carried out at the installation position of the escape path marking, in order to verify that the lighting in the aircraft cabin is sufficiently bright to be able to adequately charge the escape path marking. The illumination level is measured with a conventional luxmeter. Irrespective of the wavelength, the luxmeter records the illumination level, which is given in lux (lx). Using this method, a defined light source with a defined spectral illumination level is utilised, in order to obtain convincing measurements. Depending upon the illumination level measured, a decision is then taken about whether the escape path marking generates sufficient afterglow time for the installation position.
Aircraft cabins are in future increasingly going to be lit by means of LED light systems. The use of LED light systems with different-coloured LEDs allows for a large number of different lighting scenarios (mixed colours) and light spectra. Depending upon the relative weighting of the radiant power of the light-emitting diodes, and depending upon the model of the light-emitting diodes, very different light spectra can be present here. In the case of lighting with LED light systems, it can therefore not be determined with the aid of a one-off measurement with the luxmeter whether lighting sufficient for the stipulated afterglow time occurs.
DE 10 2009 008 526 A1 discloses a method of ascertaining the luminous flux of optical rays, in particular light-emitting diodes. The luminous flux measurement is carried out separately, without fixed filter characteristics, in parallel, in accordance with the radiometric radiant power involved and the course of the optical spectrum of radiation of an emitter, using measuring devices, on a three-port integrating sphere, by means of a power-calibrated photodiode and an uncalibrated spectrometer. Their results, linked by switching, are damped based on a modifiable luminosity table, depending upon frequency, so that, in particular for monochromatically radiating LEDs, reproducible luminous flux results can be obtained in a cost-effective way.